Conrad type ball bearings are assembled by first loading a complement of balls between the pathways of a pair of non concentric races, then moving the races to a concentric relation, spacing the balls out evenly, and finally pushing a ball retainer down into the ball complement. Each ball is forced into a separate, flexible ball pocket. It has been the practice over the last few years to integrally mold the retainers from plastic. Each pocket is generally C shaped, with a pair of retention arms that partially wrap the ball, and which, therefore, represent an undercut relative to the axis of the retainer. Still, that undercut is shallow enough, and the arms flexible enough, to allow the mold elements that form the pockets to popoout freely when the mold halves are pulled apart. This allows the retainer to be by-pass molded, that is, to be molded by a single pair of mold halves that part along the axis of the retainer. Also, because of the nature of a Conrad bearing, the adjacent retention arms of adjacent pockets have a significant circumferential gap between them. In one sense, it is desirable not to block those circumferential gaps with any other part of the retainer structure, as that would interfere with the the free flexing of the retention arms as the balls enter the pockets. In another sense, it is desirable to block those circumferential gaps, so as to keep the balls from hanging up in the gaps when the retainer is pushed in place.
The conventional response to these competing concerns had been to mold the retainer with upstanding fingers or projections in the circumferential gaps, which occupy some of the gap. The fingers exclude balls from hanging up, but do not prevent the arms of the retention pockets from flexing, since do not touch the arms. The fingers also have no undercuts relative to the axis of the retainer so the retainer can be by-pass molded. A good example of such a structure may be seen in USPN 3,749,461 to Liss et al. A finger 26 projects up in the gap between each pair of adjacent retention arms 22. But, finger 26, since it touches neither arm 22, in effect divides one circumferential gap into two. There is still not a circumferentially complete path to smoothly guide balls out of the gaps and into the pockets. The retainer disclosed in USPN 4,420,195 to Christen, assigned to the present assignee, does provide a circumferentially complete guiding path to either pocket, and does so without jeopardizing pocket flexibility. This is achieve by providing a peaked roof, in effect, over each gap, which slopes down from a central peak to each adjacent pocket. But the retainer is molded with a radial hollow below the roof. Balls inevitably see one side or the other of the peak of the roof, and are thus guided down along a complete path to one pocket or the other. As the balls enter the pocket, the flexing of the arms closes up the hollow, and the two sides of the roof flex down about the peak. This design, however, cannot be by-pass molded, and mold slides would have to be provided to create the necessary hollows. This would inevitably be more expensive than by-pass molding.